1. Technical Field
The present invention relates to a well intervention system and apparatus, in particular a subsea well intervention system and apparatus.
2. Background Information
Current estimates suggest that there are more than 4,750 subsea wells in place globally for the production of hydrocarbons from subterranean reservoirs, with ever increasing numbers year on year. As fields mature, operators are becoming more interested in reservoir recovery, well integrity and life of field planning, which leads to an increase in well intervention requirements.
There is a significant desire within the industry for intervention systems which are genuinely light weight, yet still provide an operator with a full suite of intervention capabilities. Current systems which are considered as light weight, however, have some drawbacks. For example, current systems which are promoted as being light weight are typically performed from Category A vessels which are quite highly specialized and thus might have limited availability and demand increased rental fees. Further, such Category A deployed intervention systems have limited capabilities and are normally restricted to wireline operations and in shallower water depths. Further, such systems may be associated with increased well control risks.
Where an operator requires intervention operations which exceed the capabilities of Category A run interventions, the current primary option is to utilize very heavy weight Category C rig based interventions. The Category C rig vessels are limited in number, and thus can demand very significant rental fees. Also, the limited availability of such vessels might result in significant delays in field operations, and in extreme cases might require periods of well inactivity and thus losses in revenues. Furthermore, the equipment and infrastructure associated with such heavy weight rig based interventions can be extremely costly. In some cases operators could consider the costs of intervention to be so prohibitive that the decision could be taken to abandon the well.
Also, as the majority of well intervention operations are performed on mature wells, operators are very cautious in ensuring that the type of intervention system used will minimize the risk of damaging or compromising the aging assets. This cautious approach is also driving the demand for genuine light weight well intervention systems which can support a wide spectrum of intervention operations.
Also, any intervention system must meet and indeed exceed all the necessary legislation requirements for safety and well control. As such, the individual components must be of a robust and reliable design, minimizing the risk of failure.